Patent GB-469733-A (GB)
Title: Improvements in and relating to the cutting of gear wheels
IPC: B23F5/20
Filed: 1936-01-27
Abstract: 469,733. Gear-cutting. KLINGELNBERG, G. A., KLINGELNBERG, W. H., and KLINGELNBERG, H. W. Jan. 27, 1936, No. 2571. [Class 83 (iii)] In a process for machining bevel gears with curved teeth a rotary cutting or grinding tool is swung during operation about the basic crown gear centre to generate the teeth and has in addition a supplementary rectilinear movement tangential to a circle concentric with the basic crown gear. In one form a conical cutting or grinding hob 1, Fig. 1, producing a curved bevel gear a performs the following movements : (1) Rotation about its axis ; (2) a rolling movement relatively to the blank above the imaginary crown gear centre O ; (3) a rectilinear movement in the crown gear plane along the double arrow d. These three movements also determine the speed of revolution of the work, the resultant rotation produced by the first two movements being accelerated or retarded according to the direction of the movement d. Since the cutting teeth are continually taking up fresh positions along the line d a smoother cut is obtained than when the movement is not used. In a modification a short cylindrical hob may be employed. In another modification a disc cutter may be employed, the gear in this case being formed tooth by tooth with intermittent indexing. The inclination of the line d, Fig. 5, to the cutter axis may be varied to cut teeth of different spiral angles, smaller spiral angles being preferably used for gears of larger face width. In a machine, Fig. 6, for performing the process the cutter on spindle 2 is driven from the motor 3 through gearing 82 shaft 9, gearing 87, shaft 89, bevel gears 90, and shafts 91, 93. A double worm drive 95, 96 from this shaft serves to prevent backlash in the cutter movement. The crown wheel movement is imparted to the cutter from the shaft 9 through worm gearing 8, gears 107-109, and worm shaft 31, gears 32 .. 34 and worm gear 10 on the cutter cradle 11 which rotates about axis of shaft 9. The work spindle 5 carrying the blank 4 is driven in unison with the cutter from the shaft 9 through bevel gearing 6, 7, differential gear 50, shafts 99, 19, differential gear 18, shafts 29, 101, bevel gears 102, shaft 51, and further gearing, Fig. 6, operating a worm wheel 56 on the work spindle. The crown wheel movement of the cutter cradle is compensated in the work rotation through the worm gear 103 which drives the casing of the differential 50. The cradle carries a member 12 rotatable about a journal 13 and provided with a tool slide 14 carrying a tool head 16 and traversed by a screw 15 to give the tool movement along the line d. This movement is derived from a hydraulic cylinder 17 whose piston operates the casing of the differential gear 18, the casing being connected by spur gears 20-22, wheel 23 loose on the cradle, spur gears 24 ... 26 and bevel gears 27, 28 to the screw 15. The differential 18 also transmits compensating rotation to the work through the shaft 29. When using a disc cutter a dividing head 74 is employed for indexing the blank after such reciprocation along the line d. For this purpose a shaft 42, Fig. 7, in the work driving train is disconnected from the shaft 51 by a coupling 41 and the shaft 51 which now has only the compensating movements imparted by the differential gears 50 and 18 is connected by a casing 52, pawl 53, dividing plate 54, wheels 48, 49, and worm gearing 55 to the work. The indexing motor 74 is under constant hydraulic pressure and the work is indexed one tooth through the gearing 74b when the pawl 53 is disengaged. To compensate backlash which would tend to upset the relative positions of work and tool when the movement d is reversed the worm shaft 55 is axially movable within adjustable limits by means of a hydraulic cylinder 57, the piston of which is reversed synchronously with the piston 17 producing the supplementary movement d. The member 12 has a hydraulic cylinder 60 with a constant pressure acting on its piston to hold the carriage 14 tightly against the screw threads and prevents backlash in the screw-and-nut gearing operating the carriage. Another hydraulic cylinder 67 urges the cutter-head axially against gauge members 68 associated with a stop screw 69 to determine the depth of cut and to hold the cutters up to the work. The depth of cut mechanism may be associated with a cam 72 which may be oscillated by a branch transmission from the gearing which imparts the supplementary motion d so that the teeth are cut deeper at the ends than in the middle to produce a crowned tooth form, the position of the crown along the tooth being variable. The machine may also be used for cutting spur gears. For this purpose the work table 65 is swung about the axis 66 and a wheel 76 on a feed screw 75 is brought into mesh with a wheel on shaft 77 and the shaft 79 is disconnected from the cradle drive and connected to drive the shaft 77. In this way the spindle 75 imparts the usual axial feed to the work. Interchangeable tool heads 16, 16a may be mounted on the carriage 14 the former carrying conical or concave surfaced cutters and the latter cylindrical cutters. Grinding wheels may be used instead of cutters. For cutting spur gears the movement d, Fig. 11 may also be employed to give a tangential feed of the hob past the work which has no axial feed in this case. For cutting bevel gears with off-set axes the work head 62 is vertically adjustable on a guide 63.